I'm going hiking in Bolivia, and I'm thinking about using an emergency blanket instead of a sleeping bag. Thoughts? Any recommendations on a liner or material?

Paul, it is certainly possible to hike or travel with an emergency blanket in lieu of a sleeping bag. You could buy the Space All-Weather Blanket ($14), wear all of your clothing to sleep, and in many cases stay warm.

But if that were a good option, everyone would do it. It's not: Emergency blankets are designed to reflect body heat back toward you, and they don’t have any insulation. Nor are they comfortable. They’re crinkly and stiff.

But here's the real problem: They don’t even save much weight. The All-Weather Blanket weighs 12 ounces, or two-thirds of a pound. But Mont-Bell’s 30-degree U.L. Super Spiral Down Hugger #3 bag weighs 1 pound 5 ounces, only nine ounces more. And with 800-fill, the Mont-Bell is far warmer and more comfortable. It’s not an act of desperation to climb inside—it’s an act of coziness. It gets cold in Bolivia, and staying warm counts for a lot when you're traveling.

It's true that the Mont Bell bag costs $294, so the e-blanket wins big economy points. You could save a few bucks with Marmot’s Arroyo ($260), also rated to 30 degrees, though it’s a few ounces heavier. Mountain Hardwear’s $190 Ultralamina is rated to 32, but it has synthetic filling and is neither as light nor as compressible as down. It weighs two pounds, although that isn’t bad.

These days, I also always recommend a silk bag liner like the Cocoon Silk Mummy Liner ($50). It adds five degrees or so to the bag rating, or stands alone as a light bag in warm weather. But the big advantage is that it keeps your main bag much cleaner, extending its life.